446 Field Museum of Natural History — Zoology, Vol. XL 



The hairs of Bats often show a decided difference in structural 

 characters in members of different families. In some species of Mo- 

 lossidce, for example, the hair when viewed under a powerful microscope 

 shows zones or rings of verticulate spinules (Fig. a), while in many 

 species belonging to the family Vespertilionidce the spinules or scales are 

 arranged in a continuous spiral (Fig. b), or in irregular imbricated tri- 

 angles (Fig. d). Judging from a number of specimens I have examined, 

 while the hairs of Bats belonging to allied species seem to be of the 

 same general pattern, they are by no means alike and there is usually 

 considerable variation even in hairs from the same animal. 



Hairs of Bats, 

 a, Nyctinomus depressus; b, Pipistretlus siibflavus; c, Myolis californicus: d, Lasionycleris nocii- 

 vagans; e, Corynorhinus macrolis. (Greatly enlarged.) 



Bats differ widely in appearance and mode of life from other mam- 

 mals and their place in Nature was a debatable question among the 

 older naturalists. Aristotle defined thein as birds with skinny wings; 

 Pliny also considered them birds, although he states that the young 

 are born alive and suckled by the mother. Later writers recognized 

 them as mammals, but differed as to their classification. Linnteus 

 ranked them with the Primates on account of the number of upper 

 incisors (supposed at that time to be always 4), the thoracic position 

 of the inamniffi, the placental, uterine, and other anatomical char- 

 acters. Prof. Huxley, however, later considered them to be merely 

 greatly modified Insectivora but representing a well marked order, 

 and his opinion has generally been accepted by modern zoologists. 



Bats are gregarious, nocturnal and crepuscular. They sleep most 

 of the day gathered together in dark places, such as caves, hollow trees 

 and in old buildings. When at rest they usually suspend themselves 

 by the claws of their hind feet and hang head downward. They 

 are unable to move about on the ground except with much difficulty, 

 largely on account of the peculiar structure of their hind legs (the 

 knee bending backward instead of forward), and Avhen forced to do 



